The superfamily of serotonin receptors (5-HT) includes 7 classes (5-HT1-5-HT7) encompassing 14 human subclasses [D. Hoyer, et al., Neuropharmacology, 1997, 36, 419]. The 5-HT6 receptor is the latest serotonin receptor identified by molecular cloning both in rats [F. J. Monsma, et al., Mol. Pharmacol., 1993, 43, 320; M. Ruat, et al., Biochem. Biophys. Res. Commun., 1993, 193, 268] and in humans [R. Kohen, et al., J. Neurochem., 1996, 66, 47]. Compounds with 5-HT6 receptor antagonistic activity are useful for the treatment of various disorders of the Central Nervous System and of the gastrointestinal tract, such as irritable intestine syndrome. Compounds with 5-HT6 receptor antagonistic activity are useful in the treatment of anxiety, depression and cognitive memory disorders [M. Yoshioka, et al., Ann. NY Acad. Sci., 1998, 861, 244; A. Bourson, et al., Br. J. Pharmacol., 1998, 125, 1562; D. C. Rogers, et al., Br. J. Pharmacol. Suppl., 1999, 127, 22P; A. Bourson, et al., J. Pharmacol. Exp. Ther., 1995, 274, 173; A. J. Sleight, et al., Behav. Brain Res., 1996, 73, 245; T. A. Branchek, et al., Annu. Rev. Pharmacol. Toxicol., 2000, 40, 319; C. Routledge, et al., Br. J. Pharmacol., 2000, 130, 1606]. It has been shown that typical and atypical antipsychotic drugs for treating schizophrenia have a high affinity for 5-HT6 receptors [B. L. Roth, et al., J. Pharmacol. Exp. Ther., 1994, 268, 1403; C. E. Glatt, et al., Mol. Med., 1995, 1, 398; F. J. Mosma, et al., Mol. Pharmacol., 1993, 43, 320; T. Shinkai, et al., Am. J. Med. Genet., 1999, 88, 120]. Compounds with 5-HT6 receptor antagonistic activity are useful for treating infant hyperkinesia (ADHD, attention deficit/hyperactivity disorder) [W. D. Hirst, et al., Br. J. Pharmacol., 2000, 130, 1597; C. Gérard, et al., Brain Research, 1997, 746, 207; M. R. Pranzatelli, Drugs of Today, 1997, 33, 379]. Patent application WO 01/32646 describes sulphonamides derived of bicycles, with 6 members each, aromatic or heteroaromatic with 5-HT6 receptor antagonistic activity. Patent application EP 0733628 describes sulphonamides derived of indole with an 5-HT1F receptor antagonistic activity useful for treating migraines. In general, the study of the scientific literature and patents indicates that small structural variations give rise to agonist or antagonist compounds of various receptors of serotonin that are useful for treating different diseases, depending on the receptor for which they show affinity.
After laborious research the inventors have managed to synthesize new compounds with the general formula (I) that show interesting biological properties making them particularly useful for use in human and/or veterinary therapy.